As a Watcher, I was allowed access to many of Medivh's personal effects. Among those items, I found the tomes most enlightening. While the majority of the books were filled with - to put it bluntly - tripe, there were some gems. One of those tomes documented the creation of a set of armor fit for an archmage: Frostfire.

<Angela points to her head.>

It's all in here and I am willing to share the fruits of that knowledge with you as long as you are able to provide me with the necessary materials.

Desecrated Circlet drops off Thaddius in the Abomination wing of Naxxramas, Wartorn Cloth Scraps drop off trash mobs in Naxxramas, Nexus Crystals created by disenchanting epic items, and Mooncloth is crafted by Tailors.